Human transforming growth factor alpha: sequence analysis of the 4.5-kb and 1.6-kb mRNA species.

Two transforming growth factor alpha (TGF alpha) mRNA species with the apparent sizes of 4.5 and 1.6 kb were identified in all human cell lines analysed. The cDNA corresponding to the 4.5-kb species was entirely sequenced, revealing the presence of a 3'-untranslated region (3'-UTR) of 3571 nucleotides, which contained several potential polyadenylation signals. Our results indicate that the 1.6-kb species is derived from the same precursor by alternative polyadenylation. In addition, we present evidence suggesting that TGF alpha-specific mRNAs could be initiated from transcription start points (tsp) located upstream from the tsp previously identified by Jakobovitz et al. [Mol. Cell. Biol. 8 (1988) 5549-5554].